Quantum Cloning: Difference between revisions

Quantum Cloning (edit)

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 ==Properties==
-All QDS protocols are divided into two phases, distribution and messaging. Distribution phase enables sender to generate private keys (kept secret with sender) and public keys (information distributed to recipients) while messaging phase enables exchange of messages using the above keys. For simlicity, most protocols use the case of three parties, one sender (Seller) and two recipients (Buyer and Verifier) exchanging one-bit classical messages signed by Quantum Digital Signatures (QDS).
+*'''Universal:''' A quantum cloning machine can be universal, meaning that it can copy all the possible input states equally and that the cloning machine is independent of initial states.
+*'''Optimal:''' A quantum cloning machine can be optimal which means that the average [[fidelity]] of the copies with the original state(s) is maximum over all the possible states and there is no better machine allowed by quantum mechanics for the same setting.
-*A QDS scheme is correct if a message signed by a genuine sender is accepted by a recipient with unit probability.
+*'''Symmetric/Asymmetric:''' A symmetric quantum cloning machine produce the copies which are equally well and close to the original state(s). In other words, the fidelity of all of the copies are the same. In asymmetric cloning machines instead, the fidelity of the output cloned states are different.
-*A QDS scheme is secure if no one but the sender can sign a message such that it is accepted by a recipient with non-negligible probability.
-*'''Transferability''' means that at any point a recipient (buyer) can prove it to another recipient (verifier) that the concerned message has been signed by the claimed sender (Seller).
-*'''Unforgeability''' ensures that a dishonest recipient (buyer) can neither alter a DS nor sign a message with a fake DS (DS that has not come from a genuine sender) and forward it to other recipients (verifier) successfully.
-*'''Non-Repudiation''' implies that at any point a dishonest sender (seller) cannot deny having signed the message sent to a genuine recipient (Buyer).
 ==Discussion==
 #[https://www.semanticscholar.org/paper/Unconditionally-Secure-Quantum-Signatures-Amiri-Andersson/2c9a298c9e902c5162496cc13f5d560427873412 AA (2015)] Discusses various classical and quantum digital signature schemes
 #Wallden P. (2018) (In preparation): Discusses the development of Quantum Digital Signatures from the first protocol by Gottesman and Chuang, elaborating advancements in further protocols to turn it into a practical QDS scheme.